The European Union has told Serbia that, if it wants to eventually join the EU and NATO, it will have to cooperate fully with the international war crimes tribunal in The Hague.

EU officials are insistent that Serbia must take steps toward capturing 16 men indicted by the tribunal for war crimes during the Balkan wars of the 1990s. They include the former Bosnian Serb military commander, General Ratko Mladic, who is believed to be hiding in Serbia.

But that demand puts Serbian Prime Minister Vojislav Kostunica in a difficult position. His government depends on support from the Socialists of former Yugoslav strongman Slobodan Milosevic, who is himself standing trial in The Hague for war crimes.

European diplomats said Mr. Kostunica, who held talks Tuesday in Brussels with top EU and NATO officials, promised what they described as discreet cooperation with the tribunal. They quoted him as telling EU officials he is willing to cooperate with the court in a way that will not destabilize institutions in Serbia.

But that is not likely to satisfy either the EU or NATO. Serbia is the larger part of the country of Serbia and Montenegro, the state that replaced Yugoslavia. It wants to conclude a trade agreement with the EU and is seeking to join a NATO military cooperation program known as the Partnership for Peace, as initial steps toward its eventual integration into pan-European institutions.

Another obstacle to Serbia and Montenegro's desire for closer ties to NATO and the EU is the renewed violence in Serbia's Kosovo province. Five years after the war in Kosovo began, the province, which is now under international rule, is again the scene of clashes between its ethnic Albanian majority and its Serb minority. Twenty-eight people died in violence there last week.

Mr. Kostunica has proposed dividing the province into ethnic cantons to protect the rights of Serbs. But EU foreign policy chief Javier Solana told him that such a plan would lead to an eventual partition of the province and end hopes of an ethnically mixed Kosovo. Still, Mr. Kostunica is seeking more autonomy for Kosovo's Serbs. "The Serbian government is against anything looking to [leading to the] division and partition of Kosovo. It is looking just for new institutional devices in some form of autonomy that will make the living, or the surviving, of Serbs and non-Albanians better. That's it," he said.

Mr. Solana, who is traveling to Kosovo on Wednesday, acknowledges that the safety of Kosovo's Serbs must be improved. "The fact is that minorities, in particular the Serbian minority, have not been well protected in Kosovo. And from that fact we have to make the analysis of how to do things better," he said.

Both Mr. Solana and Mr. Kostunica are against any rush to decide Kosovo's final status.

That is in stark contrast to the position adopted by the province's ethnic Albanian leadership. In an interview Tuesday with the Italian daily Corriere della Sera, Kosovo's provincial president, Ibrahim Rugova, said Kosovo must become independent and that the time has come for power to be transferred from the international administration to the Kosovo parliament.